The incorporation of flavorants in tobacco products is an important development in the tobacco industry due to the lowered aromaticity of the available tobacco and the increased preference of smokers for filter cigarettes and low delivery cigarettes.
The use of carboxylic acid and ester flavorants for tobacco products has received acceptance because of the desirable aroma and flavor characteristics which they impart to the smoke (J. C. Leffingwell, H. J. Young, and E. Bernasek, "Tobacco Flavoring for Smoking Products", R. J. Reynolds Tobacco Company, Winston-Salem, 1972). Specifically, acetic acid is commonly used as an ingredient of a Latakia tobacco flavoring formulation (J. Merory, "Food Flavorings", AVI Publishing Company, Incorporated, Westport, Conn., page 420, 1968). Isovaleric acid and 3-methylvaleric acid are major ingredients in a Turkish tobacco flavor formulation (R. H. Stedman and C. D. Stills, U.S. Pat. No. 3,180,340). Desirable flavors have been imparted to cigarette smoke by the addition of 4-ketoacids to tobacco (W. A. Rohde, U.S. Pat. No. 3,313,307).
Numerous methods of adding flavorants to tobacco smoke are known. However, none of the known methods has been found to be completely satisfactory, particularly when the flavorant is a low molecular weight carboxylic acid or ester. Specifically, some of these acids and esters are highly volatile and possess objectionably strong odors that render them difficult to use in bulk amounts required for manufacturing purposes. In addition, some of the volatile acids and esters may impart an undesirable pack aroma.
In an attempt to alleviate some of these problems, carboxylic acids have been incorporated in tobacco as part of a compound (i.e., an organic acid release agent) in such form that upon burning of the tobacco the compound will liberate one or more organic acids imparting a selected and desired flavor and aroma to the smoke. While considerably more satisfactory than earlier attempts, even this technique has evidenced certain drawbacks.
U.S. Pat. No. 2,766,145 through U.S. Pat. No. 2,766,150 describe a variety of methods for treating tobacco with compounds that release carboxylic acids on pyrolysis. The U.S. Pat. No. 2,766,145 patent describes esters of monohydric and polyhydric compounds. The hydroxy compounds may be aliphatic or aromatic in nature.
The U.S. Pat. No. 2,766,146 patent describes esters of a sugar acid selected from aldonic acids and uronic acids. U.S. Pat. No. 2,766,150 describes nonvolatile synthetic polymers or condensation products, preferably those related to polyvinyl alcohol and vinyl alcohol-type condensation products. On pyrolysis, the carboxylic acid is liberated to flavor the smoke. These polymers have a distinct disadvantage in that they generally have high molecular weights and are difficult to solubilize for application on tobacco.
Other references which disclose tobacco flavorant compositions that release carboxylic acids on pyrolysis include U.S. Pat. Nos. 4,036,237 and 4,171,702.
In a similar manner, the incorporation in tobacco of flavorants in the form of clathrates has been tried and found to be unsatisfactory, since the yield of flavor when tobacco containing such clathrates is burned is very low.
Further, as described in U.S. Pat. No. 3,782,391 alkyl esters of beta-methyl valeric acid are known to impart a fruity, apple-like aroma and a nut-like flavor when incorporated in tobacco. However, as noted in U.S. Pat. No. 3,854,485, such flavorant compounds are relatively volatile substances with a low odor threshold, and they present an evaporation problem in prolonged storage of the flavored tobacco compositions. Other esters such as monoesters of monoalkyl and dialkyl malonates are known to provide a tobacco smoke with a fermented apple-peel and walnut-like flavor and aroma, but such esters yield only a limited degree of flavor enhancement in tobacco products.
There remains a need for smoking compositions with enhanced flavor and aroma that do not exhibit the various disadvantages of prior art smoking compositions which contain a relatively volatile compound as a flavorant additive.
Accordingly, it is a main object of this invention to provide tobacco and non-tobacco smoking compositions which have incorporated therein a flavorant additive which is characterized by low volatility and low pack aroma.
It is another object of this invention to provide smoking compositions of tobacco and non-tobacco materials containing a polymerizable or polymerized malonate ester flavorant additive, which smoking compositions are adapted to impart flavor and aroma to the mainstream and sidestream smoke under smoking conditions.
It is a further object of this invention to provide polymerizable and polymerized malonate diesters which are suitable as flavorant additives for smoking compositions, which when subjected to pyrolysis conditions release monoesters and other volatile constituents which enhance the flavor and aroma of smoking compositions.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.